Method of making pistons



Patented Dec. 7, 1937 METHOD OF MAKING PISTONS George H. Blettner,Chicago, Ill., assigner to Renette Company, Chicago, Ill., a corporationof Illinois original application Maren z, 1935, serial No.

8,987. Divided and this application March 12,A

193s, serial No. 68,473

(c1. zz-zol Claims.

The present invention relates to a method of making pistons, and moreparticularly to pistons for internal combustion engines, andcontemplates the manufacture of pistons in multiple.

5 The present invention relates to a method of making pistons in suchmanner as to enable piston manufacture in quantity lots on a productionbasis, whereby the manufacturing cost per piston may be materiallyreduced.

Another object of the present invention has to do with a novel method ofcasting pistons wherein an excessive supply of molten metal is utilizedfor supplying metal to the heavier sections of the piston castings whilecooling.

l5 A further object of the present invention has to do with a novelmethod of casting pistons in multiple, with the pistons cast inhorizontal position and the skirtsof the pistons extending away fromeach other, and furthermore the supzo plying of metal to the skirts andheads of the pistons, during the cooling, to compensate for,crystallization shrinkage.

A still furtherv object of the present invention is to provide a novelmethod of manufac- ,5 turing-pistons for considerably shortening thetime required for the casting operations, land which method produceslarger production yield per mold per day, and which produces castings inwhich the physical structure ofthe metal is ,o Aof relatively ne grainand relatively uniform throughout the pistons.

'Ihe invention has for a further object the provision of a novel methodoi casting internal combustion engine pistons in horizontal posi- ,z5tion and in multiple.

' Generally speaking, the method of the present invention contemplatescasting pistons in multiple, with the pistons horizontally cast; and soarranged that the pistons are cast in `pairs or in 4 l groups of pairs,with the heads of the pairs adjacent each other, and an ingate providedwith expansion provision, suiiciently close to the castings to supplymetal to the heavier sections of the pistons while cooling and to be inheat transfer relation with the piston castings in the mold cavities Theinvention contemplates the formation voi present invention may bepracticed, and the views thereof are as follows:

Figure 1 is a side elevational view of one of two cooperating moldsections, in casting position, with the cores in place, and illustratingone man- 5 ner of supporting the cores, and indicating, fragmentally,means for moving the cores into and out of casting position. f

Figure 2 is an axial sectionalview of a mold section, with the cores inelevation, and showing, 10 in section, the cast pistons, the ingate,expansion ball, risers, and sprue, and illustrating the manufacture ofpistons in multiple in accordance with the present invention.

Figure 3 is a transverse vertical sectional View 15 through theillustrated form of mold, and a cast piston, showing core prints inplace for forming the wrist pin holes in the bosses. In thisi'lgure,'the core is removed, for clearness.y

'Ihe drawing will now be explained. l The present invention is adivision of copending application, Serial No. 8,987, led March 2,v

The' illustrated form of mold consists of two sections, A and B, whichare adapted to be moved against and away from each other. 'I'he sectionsare shown as hingedly connected bymeans of legs I and 2 on the sectionsA and B respectively, which legs, in turn, are secured by bolts 3 and 4to flanges 5 and 6 of a hinge which comprises' o eyes 'I and 8 receivinga pintle pin 9. The mold may be mounted in any convenient manner forready operation.

'I'he sections A and B are counterparts; therefore the description ofone will suflice for both.

'I'he section A is shown as provided `with two horizontally' disposedsemi-cylindrical cavities, which are axially spaced and horizontallydisposed, with the outer ends of the cavities opening through the endsof the section. Riser cavi- 40l Vties II of relatively shallow depth arealso provided, as well an ingate I2, which is illustrated as fashionedwith an enlargement or expansion ball I3 disposed between the -pistoncavities Ill and communicating with these cavities bymeans of u,

passages Il. The lower end of the ingate I2, is shown, in the presentembodiment, as communicating with axiallyextending cavity or sprue I5,which also supplies molten metal from the ingate to the bottoms of thepiston cavities I Il. The sprue cavity I5 is shallow, as may be observedin Figure 3.

Each mold section, A and B, is provided at its ends with asemi-cylindrical seat I6 for receiving and encompassing the cores whichare inserted l endwlse into the mold cavities ill by axial movement.

y Each of the mold sections is provided with an upstanding head or neckII which, when the sections are together in casting position, coop-Vcrate to form a bullet mold entrance for the ingate. These necks I1extend above the mold sections to provide, in the ingate, a head ofmolten metal tocompensate for crystallization shrinkage as the castingscool.

It is of course understood that when the sections A and B are broughttogether for casting purposes, thesemi-cylindrical cavities I9 cooperateto form cylindrical cavities, and the ingate, sprue, and riser cavitiesin each section cooperate with the corresponding parts in the othersection to complete the mold.

vThe cores herein illustrated are the metallic cores of the aforesaidcopending application, but it is to `be understood that the cores couldbe of sand or otherwise,l to conform to the characteristics of the metalutilized for casting pistons.

The cores herein illustrated are designated respectively as C and D, andare adapted to enter the piston cavities III by endwise movement intothe cavities. lindrical portions I8 which enter the cylindrical portionsformed by the closing of the sections A and B together, thus makingthesemi-cylindrlcal portions I6 into cylindrical portions, for thusclosing the ends of the piston cavities of 'the mold.

The cores Cand D are herein shown as supported by means of rods I9,which are mounted in suitable uprights 20, carrying bearing elements 2Iand 22 for supporting the rods I9 and permitting reciprocal movementthereof in service.

The Ycores C and D, herein illustrated, as before stated', are metalcores, and therefore supporting these cores on the rods I9 enablesspeedy operation cf the cores as to insertion and withdrawal withrespect to the piston cavities of the mold.

When, however, sand cores or cores of other types are utilized, thesewould be inserted by hand, through the ends of the moldsections, whentogether in casting position, in which event the rods I9 and thesupports 20 would be eliminated.

The method of the present invention is cal'-,

ried out as follows:

Sections A and B are closed against each other to form the cylindricalpiston cavities I and the cooperating gate, sprue, and riserarrangement.

The cores C and D are then inserted in the ends of the mold, closingthese ends, and thus being properly positioned Within the lpistoncavities.v

The metal is then poured into the head I1, whereupon it passesdownwardly through the ingate, through the connections I4, the sprueportions I of the gate, and then into lthe mold cavities, and eventuallyentering the riser spaces Il. Sufiicient molten metal is supplied to themold to flll the ingate approximately to the upper extremity of the headIl, thereby assuring a sufficient head of molten metal in the ingate andthe expansion ball I3 to supply additional metal to the castings, andfor heat transfer, while cooling, to compensate for the usual shrinkage.

The provision of theenlargement of the ingate is adjacent the heaviersections of the pistons, so as to assure at all times a supply of metalto the heavier sections of the pistons, thereby affording a plentifulsupply of metal to the pistons, so that formation of cracks in thepistons is prevented. The exteriors of the pistons are fashioned by thecontours of the mold cavities I0,

The cores are fashioned with cY- while the cores C and D form theinteriors of the pistons.

When the casting operation has been completed, if the cores C and D aremetal and mounted on the rods I9, the rods are actuated to withdraw thecores from the mold, and the sections- A and B are then separated. Whenthe mold sections A and B have 'been separated, the finished product,consisting of the two pistons and such portions of the metal as may bein the ingate, sprue portion I5, and riser portions I I, and branches'I4, is then removed from the mold, and, when sufficiently cool, thescrap metal is removed from the pistons by sawing or other suitableoperation.

The piston blanks thus formed are then subjected to suitable machineoperations to bring the pistons to finished size, and also to form theusual'plston ring grooves in the head portion of the pistons.

Prior to the time of the casting operation, core prints 23 areintroduced in properly disposed apertures 24 in the sections, which coreprints form the interiors of the wrist pin bushings, that is, form thewrist pin bearing portions of the pistons. i

The method of the present invention contemplates the formation ofpistons in multiple, by casting operations, and, as illustrated herein,two such pistons are cast at a pouring. It is to be understood of coursethat the mold may be constructed to form more than two pistons at atime, multiples of two being readilyv cast in accordance with themethodof the present invention.

It has been found that the method of the present invention lends itselfreadily to -rapid production of uniform pistons so that the laborincidental to the molding operation is reduced to a minimum. The mannerof supporting the cores C and D on rods I9, or equivalent structuresreduces the time necessary for setting the cores for the castingoperation, the whole method expediting to a considerable extent theamount of time necessary for arranging the mold for casting operationand thus expediting quantity production.

The provision of the enlargement or expansion ball in the ingate,together with the risers and sprue portions of the mold is such thatevery casting formed is full, free of cracks and blow holes, and ofuniform texture throughout its extent, thin sections as well as thicksections.

When sand cores are utilized, these may be crumpled away from theinterior of the piston castings, after the castings have been removedfrom the mold.

Instead of utilizing the specific enlargement I3, as shown, in theingate, the ingate could be formed otherwise to provide a suflicientsupply of metal to the piston castings while cooling.

I am aware that many changes may be made and numerous details ofconstruction may be varied through a wide range without departing fromthe principles of this invention, and I therefore do not purposelimiting the patent granted hereon otherwise than necessitated by theprior art.

'Ihe invention is claimed as follows:

1. That improvement in the method of simultaneously casting a pluralityof internal combustion engine pistons which comprises the steps offorming a plurality of piston casting cavities in a mold with the axeshorizontal and the head forming ends of the cavities facing each other,

forming in the mold a single feeder which when the mold is in castingposition extends downwardly between and past the facing head formingends of the cavities and suillciently closely adjacent said ends to bein heat transfer relation therewith, forming in the mold a plurality ofconnections from the feeder to each cavity with one of the connectionsto each cavity opening into the cavity through a side of' the same, andsupplying molten metal to said feeder connections and cavities.

2. That improvement in the method of simultaneously casting a pluralityof internal combustion engine pistons which comprises the steps offorming in a mold a plurality of pistoncasting cavities with the axeshorizontal and the head forming ends thereof facing each other, formingin the mold a single feeder which extends iiown` wardly between and pastthe ends of said cavities and in sulciently close proximity thereto tobe in heat transfer relation therewith when the mold is in .castingposition, providing a connection from the feeder to each cavity tosupply metal through the sides of the cavities, and supplying moltenmetal to the feeder connections and cavities.

3. That improvement in the method of simultaneously casting a pluralityof internal combustion engine pistons which comprises the steps offorming a plurality of piston casting cavities in a mold with the axeshorizontal and the head forming ends of the cavities facing each other,and conducting molten metal to the cavities in a path part of which isvertical and extends downwardly between and past the head ends of lthecavities and in heat transfer relation therewith and a part of which ishorizontal and supplies metal to the sides oi' the cavities. l

4. That improvement in the method of simultaneously casting a pluralityof internal combustion engine pistons which comprises forming in a molda pluraltiy of piston casting cavities with their axes horizontal andthe head-forming ends thereof facing each other and the skirt-formingcavities extending away from each other, forming-in the mold a feederwhich extends downwardlybetween and past said ends in heat transfer'relation therewith, providing connections from said feeder to said headends and to said skirt-forming cavities, and supplying molten metal tosaid feeder for passage through said connections to said cavities.

5. .That improvement in the method of simultaneously casting a pluralityof internal combustion engine pistons which comprises forming in a molda plurality ofpiston casting cavities with their axes horizontal and thehead-forming ends thereof facing each other and the skirt-formingcavities extending away from each other, forming in the mold a feederwhich extends downwardly between and past said ends in heat transferrelation therewith, providing connections from said feeder to said headends and to said skirtforming cavities, forming a riser in said moldlengthwise of each of said skirt-forming cavities, and supplying moltenmetal to said feeder for passage through said connections to saidcavi-.- ties, with the excess of such metal owing upwardly into saidrisers.

GEORGE H. BLET'INER. 86

